1. Field of the Invention
The present invention relates to a portable terminal, and more particularly, to a portable terminal having a secondary coil for wireless charging, as well as a plurality of antenna elements.
2. Description of the Related Art
In general, a portable terminal is a device capable of performing a mobile communication function, an electronic note function, Internet access, and a multimedia function, among other functions, while being carried by a user. Recently, various functions have been integrated in a single mobile communication terminal called a smart phone.
Meanwhile, a transport card, a security card, a credit card, and the like can be used to make payment or to authenticate a user by a Near Field Communication (NFC) function. As portable terminals have become a daily commodity, they are equipped with the NFC function. Accordingly, a portable terminal is provided with an additional antenna for performing the NFC function. Compared to short-range wireless communication, such as Bluetooth™ or Zigbee™ functions, the NFC technology provides an advantage of fast communication setup between communication devices. Despite this advantage, the NFC function communicates at a relatively low frequency of 13.56 MHz, making it important to be within recognition distance to implement the NFC function in a portable terminal.
To supply power to the portable terminal, a detachable battery pack or a built-in battery pack is used. A user charges the battery pack according to the remaining amount of battery power, generally, using a separate charger. To increase user convenience, efforts have been made to commercialize wireless charging. For wireless charging, inductive coupling using a magnetic field, capacitive coupling using an electrical field, and radio frequency wave radiation are available. Among them, the inductive coupling scheme is suitable for wireless charging in terms of power efficiency. According to the inductive coupling scheme, a battery pack is wirelessly charged by aligning a primary coil of a charger with a secondary coil of a portable terminal.
To implement both the NFC function and the wireless charging function in a single portable terminal, an NFC antenna element taking the form of a loop antenna and a secondary coil for wireless charging should be mounted in the portable terminal. A shielding body is used to prevent interference between the antenna element and the secondary coil, and to protect from interference caused by the secondary coil on other circuits of the portable terminal when the antenna element and the secondary coil simultaneously operate. However, the use of a shielding body for each of the antenna element and the secondary coil increases the thickness of the portable terminal. Although the secondary coil for wireless charging may be utilized as the NFC antenna element, it is difficult to achieve both wireless charging efficiency and a recognition distance for NFC. Moreover, since the shielding body is usually formed by rolling to be in a planar form, it is difficult to fix a spirally wound coil or an antenna element having the same structure.